The present invention relates to a process for welding a weld stud onto a workpiece by means of a drawn arc.
In such a process, a weld stud is removed from contact with a workpiece in a return stroke whereby a pilot arc is struck and then returned toward the workpiece in a forward stroke during the burning of a welding arc. Our German Patent specification DE 36 11 823 describes such a process.
The known process serves to recognise and compensate welding conditions which differ from one welding point to another in order to obtain perfect welds despite finding undesirable conditions at the respective welding point. For this purpose, utilising the pilot current arc and the voltage emerging at it, the height or the duration of the welding arc is set using a correspondingly adjustable welding power supply unit as required by the conditions prevailing in each case.
It has been found that the welding of weld studs by means of a drawn arc leads to difficulties when applied to workpieces consisting of thin sheet metal and having a thickness of, for example, 0.7 mm insofar as the metal sheets are penetrated so that they are partially welded through, i.e. undesirable liquefaction of the sheet metal material occurs on the side remote from the actual welding point.
The object of the invention is to provide a stud welding process according to the foregoing details which is particularly advantageous for use on thin sheet metal, for example sheet metal having a thickness of 0.7 mm and below.